Basic Trope: A blustering braggart whose tales of his own heroism and bravery are more fiction than reality.
Straight: Miles likes to boast about how heroic he is when he gets into a fight. When he finds himself facing one, however, he runs away as fast as he can.
Exaggerated: Miles has weaved an entire legend about himself and his exploits have all but entered mythology. People throw themselves at his feet as soon as they learn who he is, and he has statues built of himself and babies and places named after him. People believe that he's the hero who will solve all their problems. Problem is, Miles has outright stolen the credit for his heroic actions from other people who for some weird reason cannot dispute his claims, and when times comes for people to truly rely on him, he lets them all down. When the crisis is resolved without his direct involvement, however, he is quick to snatch the credit and start boasting about how he was responsible for it.
Miles is a good if not excellent soldier, and prone to exaggerate his part after fights — which other soldiers take with good humor, because he's amusing at it.
Miles is a veteran soldier who has gone to seed, but acts like he is just as tough as he used to be.
Justified: Miles has been incorrectly credited with a heroic action in the past and has preferred to milk the glory that comes from it rather than confess to the truth.
Miles was telling the truth about his exploits, but he was defeated by the Big Bad easily regardless of that fact.
Double Subverted: Miles fared well in the earlier battle because he rigged it with phonies who wouldn't fight back; when placed in an actual combat situation where he doesn't control the outcome, his resolve fails him.
Parodied: Miles' stories are Blatant Lies, many lifted directly from well-known works of fiction. However, everyone around him carries the Idiot Ball and takes him at his every word.
Some of Miles' stories are true, and his competence generally fluctuates depending on the writers' whims.
Averted: Miles doesn't take credit for the actions of others or cultivate an undeservedly heroic reputation.
Enforced: "We need a rival for the hero to overcome. Someone who seems to be better than him but who can't back up his talk."
Lampshaded: "He's a fraud, but he's a fraud with credidentials."
Invoked: Miles and Peter are alone on the front line of a battle when Peter performs a heroic action while Miles cowers back. Either through the action itself or Miles' direct involvement, Peter ends up dead. As there is no one else around to deny it, Miles takes credit for Peter's heroic action and milks the reward.
Exploited: Emperor Evulz's plan relies on Miles being the hero everyone said he was. Hiro insists that Miles reveal his true cowardly self and ruin Evulz's plan.
Defied: Miles confesses the truth; he is no hero, merely someone with a good reputation.
Discussed: "I have to admit I'm suspicious of Miles; he tells a good story but he always seems to distance himself from the action as much as possible..."
Conversed: "Will these characters ever learn that the pompous braggart is always just all talk?"
Miles' stories cause people to rely on him when they really shouldn't; when he inevitably lets them down, lives are lost and ruined, and plans fail because of him. However, because the people around him are so eager to take him at his word without checking him out, they must take some of the inevitable blame.
Miles knows very well that he is not as good as he says that he is, but he has his reasons why he feels that he must try to keep his image alive and well, and is afraid of what the consequences will be if people ever found out the truth. (Though he also feels a bit guilty that he keeps trying to live a lie.)
Although Miles' incompetence and cowardice does dramatically ruin the plan, things are nevertheless salvaged — but at great cost. Miles' reputation is permanently ruined, however, and people are unwilling to believe him or his boasting ever again.
Miles makes sure that it looks like it was the civilians own fault. And everyone believes him since all who knew the truth died.
Played For Laughs: Miles' boasting is way over the top, and his eventual comeuppance results in a very satisfying Humiliation Conga.
Played For Drama:
When the people who were really responsible for Miles' 'heroism' or know the truth of what happened learn of Miles' boasting, they are outraged and driven to murderous anger. Miles ends up dead.
Miles is willing to do anything to make sure the truth doesn't come out — even murder.